Project Summary

View and print project details including project summary, purpose, associations to Biological Opinions,
and area. To learn more about any of the project properties, hold your mouse cursor over the field label.

Please correct the errors noted below.

Project 2007-063-00 - Use of drift nets to monitor production and limiting factors in recruitment of larval Pacific lamprey

Use of drift nets to monitor production and limiting factors in recruitment of larval Pacific lamprey

Summary:

The primary purpose of this proposal is to assess a larval drift protocol for general application throughout the CRB, describe local spawning stock - larval recruitment relationships, and quantify factors limiting early recruitment of Pacific lamprey.

This proposal addresses the problem of accurately assessing the abundance of early life stage lamprey larvae and developing spawner-larval recruitment relationships. The sponsors objectively discuss the advantages and disadvantages of sampling techniques including their own and conclude that the technique they propose would be better for sampling early life stages of larvae. Data on lamprey abundance are identified as a priority in the Willamette subbasin plan. The proponents have done substantial networking with other lamprey researchers in the Columbia River Basin. The latter are not using drift methodology, so the proponents could have a unique methodology that could be integrated with studies elsewhere. The proponents have laid out a measured and defensible plan to assess the drift methodology with a proof of concept approach.

Comments on Objective 1: "Establish and assess a monitoring protocol that employs larval drift sampling to gauge Pacific lamprey distribution, status, and life history in large river basins where little information exists." The proponents should assess sampling efficiency of the drift nets. As well, cross channel differences in lampreys could affect abundance estimates depending on where the three nets were deployed. It is likely that habitat impacts vary between the eight subbasins to be investigated. And it would be useful to tie this work into habitat planning as much as possible as data on flows, substrates etc could be used by others studying the Willamette basin. This would enhance the benefits of the study.

Comments on "not fundable" objective 2: "Investigate the relationship between Pacific lamprey spawning stock and recruitment to larval phase." The design for objective 2 does not mimic the natural situation that will occur in most rivers. Downstream drifting emergents may come from several spawning areas upstream, mortality would occur as they drift downstream, and some would have settled out before reaching the sampling. It would be virtually impossible to predict the number of spawners that produced the larvae captured in the drift nets. The investigators do not discuss how corrections will be made for net efficiency. Nor do they discuss the kinds of stock-recruitment models that would be appropriate. To estimate abundance of emergents it would seem simpler to just cap nests and determine the number of eggs that survive to emergence. The types of analyses that will be conducted are not given.

Comments on "not fundable" objective 3: "Describe and quantify the chief factors limiting Pacific lamprey larval recruitment in focal spawning areas." The sponsors do not explain how mortality from egg predation will be quantified. How will the affect of abiotic variables be analyzed taking into account differences in fecundity, which will not be measured? Adult predation and redd superimposition were other factors mentioned but no details on how they would be assessed were given.